1. WG3a Sources Update Jim Clarke on behalf of WG3a GDE Meeting, Frascati, December 2005

2. Baseline Recommendation –Helical Undulator Based Positron Source with Keep Alive System Alternative Study Recommendation –Laser Compton Based Positron Source Additional Recommendation –Conventional Source is a backup to the undulator based source but no further R & D should be carried out on the conventional source at this time

3. Primary e - source e - DR 5 - 100 GeV e - Bypass line 2 nd e - Source 150 – 250 GeV e - Transfer Line Target e - Dump Photon Beam Dump e + DR Auxiliary e - Source Photon Collimators Adiabatic Matching Device e + pre- accelerator ~5GeV Electron Linacs 100 GeV150 GeV Helical Undulator Photon Target IP250 GeV Positron Linac Beam Delivery System Recommended Baseline Layout Undulator at end of electron main linac and with keep-alive source

4. Undulator Placement Snowmass WG3a recommended end-of-linac placement Vigorous discussion since of merits of EOL vs. mid-linac position (150 GeV) GDE White Paper – Himel, Walker & Yokoya recommends mid-linac position GDE executive accepts the recommendation –The BCD Executive Committee has agreed to accept the recommendations outlined in the recent GDE task force White Paper on the location of the undulator-positron source. The undulator source will be placed at the 150 GeV point in main electron linac. This will allow constant charge operation across the foreseen centre-of-mass energy operating range. WG3a Snowmass document has been revised to reflect this

5. Keep Alive No specification agreed at Snowmass White Paper further recommended minimum source intensity of 10% of nominal –We recommend a minimum intensity requirement of 10% of nominal intensity to reduce the chance of such systematic errors making the keep-alive source nearly useless and because there are inexpensive ideas on how to make a 10% source. This source would have all bunches filled to 10% of nominal intensity. Note that higher single-bunch intensity is better even at the expense of populating a smaller fraction of the bunch train.

6. Revised Conceptual Layout Primary e - source e - DR Target e - Dump Photon Beam Dump e + DR Auxiliary e - Source Photon Collimators Adiabatic Matching Device e + pre- accelerator ~5GeV 150 GeV100 GeV Helical Undulator In By-Pass Line Photon Target 250 GeV Positron Linac IP Beam Delivery System

7. E-166 Experiment E-166 is a demonstration of undulator-based production of (polarized) positrons for linear colliders: - Photons are produced ~in the same energy range and polarization characteristics as for ILC; -The same target thickness and material are used as in the linear collider; -The polarization of the produced positrons is the same as in a linear collider. -The simulation tools are the same as those being used to design the polarized positron system for a linear collider. A Mikhailichenko, Cornell

8. E -166 Proof of Principle Experiment at SLAC First run before Snowmass successful –Positrons generated –Polarisation measured Second run after Snowmass –Data taken over wider energy range –Many more events recorded –Analysis ongoing

9. E-166 at SLAC Undulator table Positron table Gamma table Vertical soft bend Undulator table Positron table Gamma table Vertical soft bend A Mikhailichenko, Cornell

10. E166 Status E166 Collaboration meeting Nov 7-9 in DESY-Zeuthen Positron and Photon asymmetries are calculated – reasonable agreement with expected values Need to understand analyzing power of the photon and positron analyzers magnets to convert to polarization values Presentation of preliminary results in ECFA meeting in Vienna Experiment expected to be fully analyzed by Spring 2006 V Bharadwaj, SLAC

11. Undulator Technology Helical Collaboration in UK Permanent Magnet and Superconducting examined –20 period models built SC now selected for further development because has several proven advantages: –Able to vary field levels easily –Able to switch off modules –Quality high –Cheaper Daresbury & Rutherford now collaborating with Cornell

13. Long Superconducting Prototype Design Amanda Brummitt, RAL Cryostat length – 4000 mm Undulator length (incl. ends) – 3576 mm (89%) Undulator effective length – 3480 mm (87%)

14. Ongoing Evaluation of Parameters

15. Target Work Active collaboration between SLAC, LLNL, Daresbury and Liverpool Forces on rotating target due to B field calculated by LLNL (preliminary report produced) R & D plan including prototyping being firmed up

16. Spin Tracking Ongoing program of studies for ILC Results for Damping Rings confirmed earlier results for 6km & 17km rings Presented at Nov 2005 DR Workshop

17. Latest Undulator Layout 500MeV electron keep alive source

18. Summary Undulator moved to 150 GeV Keep alive source specified E-166 second run completed succesfully Superconducting technology selected Target R & D ongoing Spin Tracking advice presented at Damping Rings workshop All interested global teams are working together on design solutions –Others are welcome to join in !